JPH07105647B2 - Ferromagnetic thin film filter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ferromagnetic thin film filter using a ferromagnetic thin film element such as YIG.

[Outline of Invention]

The present invention relates to a ferromagnetic thin film filter, in which a pair of ferromagnetic thin film elements are formed on both main surfaces of a non-magnetic substrate so as to face each other, and a magnetic field perpendicular to the film surface is formed on the pair of ferromagnetic thin film elements. The input and output lines are coupled to this pair of ferromagnetic thin film elements, which effectively increases the volume of the ferromagnetic thin film, especially its thickness, improving the insertion loss and improving the 3 dB bandwidth. Is intended to be expanded.

[Conventional technology]

A filter using a conventional ferromagnetic thin film such as YIG (for example,
In JP-A-59-103403), it is necessary to apply a bias magnetic field to the ferromagnetic thin film by using a permanent magnet or an electromagnet. Magnetic devices for this purpose are described in Japanese Patent Application Nos. 59-44244 and 59-180941.

A conventional ferromagnetic resonance device will be described below with reference to FIGS. 5 and 6 (a cross-sectional view taken along the line VI-VI in FIG. 5). This is a two-stage filter using a YIG thin film as a ferromagnetic thin film element. Reference numeral (1) is a quartz substrate as a dielectric substrate, and a ground conductive layer (2) is formed over the entire back surface of the quartz substrate. Near the both sides on one main surface of the quartz substrate (1), first and second parallel and mutually opposite directions are provided.
Input and output side microstrip lines (3), (4) are formed by deposition, and the opposite ends of the microstrip lines (3), (4) are connected to the dielectric substrate (1) and the GGG plate (7). Then, it is extended and connected (short-circuited) to the ground conductive layer (2). (3a) and (4a) are short-circuited ends of these microstrip lines (3) and (4).

(7) is a GGG (gadolinium gallium garnet) plate (for example, 400 μm) as a non-magnetic plate, on which a YIG thin film is formed on both main surfaces by a liquid phase epitaxial growth method, and on one of the main surfaces. The YIG thin film is etched using photolithography, which allows, for example,
Disc-shaped YIG thin films (5) and (6) having a diameter of 1.5 to 3 mm and a thickness of 30 to 50 μm are deposited on one main surface of the GGG plate (7). In this case, the YIG thin film deposited on the other main surface of the GGG plate (7) is entirely removed. Then, on the other main surface, at both ends of the YIG thin film (5),
A microstrip line (8) for connection is adhered and formed so as to face (6), and both ends of the microstrip line (8) are extended after bonding the dielectric substrate (1) and the GGG plate (7) to form a ground conductive layer ( 2) is connected (short-circuited). (8a) and (8b) are
These are both short-circuited ends of the connecting microstrip line (8).

Then, the deposited G of the YIG thin films (5) and (6)
Each of the YIG thin films (5) and (6) of the GG plate (7) is short-circuited on the input and output side microstrip lines (3) and (4) deposited on the quartz substrate (1). (3a),
Quartz substrate (1) and GGG so as to adhere to the vicinity of (4a)
The plates (7) are laminated together.

The device shown in FIG. 5 and FIG. 6 is arranged in the gap of the magnetic device, and the YIG thin films (5) and (6) are made uniform in a plane perpendicular to the film surface because of their ferrimagnetic resonance. A fixed (or variable) bias DC magnetic field is applied to obtain the filter device.

FIG. 7 shows frequency characteristic curves of insertion loss and reflection loss of such a filter as 1L and RL, respectively. This is calculated. This filter is a bandpass filter having a bandpass center frequency of 1.575 GHz. in this case,
Internal Q Qu (described later) is approximately 400, External Q Qe (described later) is approximately 1
00. This filter has a minimum insertion loss of 2 dB and a maximum return loss of 19.5 dB. Also, the 3 dB bandwidth is 25 MHz.

[Problems to be solved by the invention]

By the way, the factors that determine the characteristics of the filter as the ferromagnetic resonance device are ferromagnetic thin films (5) and (6).
Internal Q (this is referred to as Qu) and external Q (including this) including loads connected through the input and output side microstrip lines (3) and (4) or the connecting microstrip line (8). Qe)). Then, the insertion loss, the reflection loss, and the 3 dB bandwidth of the filter are determined by these internal and external Q Qu and Q e. The internal Q Qu is controlled by mixing Ga and other impurities into the ferromagnetic thin films (5) and (6) and the growth conditions during the liquid phase epitaxial growth, while the external Q Qe is controlled by the ferromagnetic thin films (5) and (6) and microstrip line (3),
It is determined by the device structure such as the positional relationship with (4) and (8).

As one of the structural elements that determines this external Q Qe, there is the volume (determined by its diameter and thickness) of the ferromagnetic thin film (thin film magnetic resonator) used. That is, the external Q of the filter
Qe is inversely proportional to the volume of the ferromagnetic thin film.

However, the increase in the thickness of this ferromagnetic thin film is naturally limited for the following reason. That is, GGG board (7) and YIG
Since it is difficult to completely remove the lattice mismatch between the thin films (5) and (6), if the film thickness is made too large, damage during the YIG thin film growth process or the etching process by photolithography may occur. Will be damaged.

In view of such a point, the present invention intends to effectively increase the volume of a ferromagnetic thin film, particularly the thickness thereof, without causing damage to the ferromagnetic thin film, and achieve insertion loss and extension of the 3 dB bandwidth. It is intended to propose a ferromagnetic resonance device that can be used.

[Means for solving problems]

The ferromagnetic thin film filter according to the present invention comprises a non-magnetic substrate (7).
And a pair of first and second ferromagnetic thin films (5a), (5b); (6a), (6b) formed on both main surfaces of the non-magnetic substrate (7) so as to face each other in parallel. ) And its first and second
Of the pair of ferromagnetic thin films (5a), (5b); (6a), (6b), each of which has a ground conductive layer (2) formed on one surface thereof so as to be coupled to the dielectric substrate (1). Input and output lines (3) and (4) formed on the other surface of the first and second sets, and ferromagnetic thin films (5a) and (5b) of the first and second sets; (6a) and (6b)
A connecting line (8) arranged so as to be coupled to the first and second sets of ferromagnetic thin films (5a), (5b); (6a), (6b)
On the other hand, a magnetic device (16) for applying a magnetic field in a direction perpendicular to each film surface is provided.

[Action]

According to the present invention, the first and second sets of ferromagnetic thin films (5a), (5b); (6a), so as to face each other in parallel on both main surfaces of the non-magnetic substrate (7), Since (6b) is formed, the thickness of the ferromagnetic thin film is effectively increased.

〔Example〕

A two-stage filter as a ferromagnetic resonance device of the embodiment will be described below with reference to FIGS. 1, 2 (a sectional view taken along the line II-II in FIG. 1) and FIG. First, the device will be described with reference to FIGS. 1 and 2.
Reference numeral (1) is a quartz substrate as a dielectric substrate, and a ground conductive layer (2) is formed over the entire back surface of the quartz substrate. Input and output side microstrip lines (3) extending in parallel in mutually opposite first and second directions near both sides on one main surface of the quartz substrate (1),
(4) is adhered and formed, and its opposite ends are extended to the ground conductive layer (2) after joining the dielectric substrate (1), the GGG plate (7) and the dielectric plate (9). ) Is connected (short-circuited). (3a) and (4a) are short-circuited ends of these microstrip lines (3) and (4).

(7) is a GGG (gadolinium, gallium, garnet) plate (for example, 400 μm) as a non-magnetic plate, and YIG thin films are formed on both main surfaces by the liquid phase epitaxial growth method. A thin film is patterned by etching using photolithography on each main surface, and thus, for example, the diameter is 1.5 to 3 mm and the thickness is 30 to 50.
Disc-shaped YIG thin film (5a), (5b); (6a), (6
b) are respectively adhered and formed on both main surfaces of the GGG plate (7) so that their respective centers face each other and face each other.

Then, another quartz plate (9) as a dielectric plate is provided, and a microstrip line (8) for connection is adhered and formed on one main surface of the quartz plate (9). After joining the GGG plate (7) and the dielectric plate (9),
It is extended and connected (short-circuited) to the ground conductive layer (2).
(8a) and (8b) are both short-circuited ends of the connecting microstrip line (8).

And this YIG thin film (5a), (5b); (6a), (6b)
Each YIG thin film (5a) of the GGG plate (7) formed by
So that (6a) adheres to the vicinity of the short-circuited ends (3a), (4a) above the input and output side microstrip lines (3), (4) adhered to the quartz substrate (1), The quartz substrate (1) and the GGG plate (7) are bonded together. Further, the surface of the dielectric plate (9) on which the connection microstrip line (8) is formed, on the side where the connection microstrip line (8) is not formed (the surface on the side where it is formed is also acceptable).
To the YIG thin films (5a) and (5b); (6a) and (6b), and to the GGG plate (7) so as to cross the input and output side microstrip lines (3) and (4). To match.

Then, the device shown in FIG. 1 and FIG.
0)] is disposed in the gap G of the magnetic device (16) shown in FIG. 3, and YIG thin films (5a), (5b); (6a), (6
b), because of its ferrimagnetic resonance, given a fixed or variable bias DC magnetic field that is perpendicular and uniform to the film surface,
A filter device is obtained.

In this magnetic device (16), pole pieces (12) and (13) are provided in a magnetic yoke (14) so as to face each other, and coils (14) and (15) are wound around them, respectively. . The coils (14) and (15) are connected in series or in parallel,
A direct current is applied to this so that the pole pieces (12) and (13) are magnetized in opposite polarities. This DC current is fixed (or variable).

This magnetic device may be one using a permanent magnet instead of the electromagnet, or one using both an electromagnet and a permanent magnet.

In this case, the thickness, that is, the volume of each of the YIG thin films (5a), (5b); (6a), (6b) is substantially double that of the conventional one.

FIG. 4 shows frequency characteristic curves of insertion loss and reflection loss of such a filter as 1L and RL, respectively. This is calculated. This filter is a bandpass filter having a bandpass center frequency of 1.575 GHz. in this case,
The internal Q Qu is approximately 400 and the external Q Qe is approximately 60. This filter has a minimum insertion loss of 1.2 dB and a maximum return loss of 23.9 dB.
Is. Also, the 3 dB bandwidth is 36 MHz.

Thus, the filter as such a ferromagnetic resonance device is
The insertion loss and the extension of the 3 dB bandwidth are achieved.

The dielectric substrate (1) and the dielectric plate (9) may be replaced with each other.

Further, the number of stages of the filter is arbitrary. For example, in the case of a one-stage filter, the YIG thin films (6a) and (6b) and the output side microstrip line (4) are omitted and the connecting microstrip line (8 ) May be used as the output side microstrip line.

〔The invention's effect〕

According to the present invention described above, a non-magnetic substrate, first and second sets of ferromagnetic thin films formed on both main surfaces of the non-magnetic substrate so as to face each other in parallel, and the first and second sets thereof. Input and output lines formed on the other surface of the dielectric substrate having a ground conductive layer formed on one surface thereof so as to be respectively coupled to the second set of ferromagnetic thin films; A coupling line arranged to couple to the two sets of ferromagnetic thin films;
And a magnetic device for applying a magnetic field in the direction perpendicular to each film surface to the second set of ferromagnetic thin films, so that the volume of the ferromagnetic thin films, especially the thickness thereof, is accompanied by the damage of the ferromagnetic thin films. It is possible to obtain a ferromagnetic thin film filter capable of effectively increasing the insertion loss and the 3 dB bandwidth without increasing. Further, since the first and second sets of ferromagnetic thin films are formed on both main surfaces of the nonmagnetic substrate so as to face each other in parallel, the first and second sets of ferromagnetic thin films are provided. Nevertheless, the structure of the ferromagnetic thin film filter is not so complicated, and therefore the manufacturing process thereof is not so complicated.

[Brief description of drawings]

1 and 2 are a plan view and a sectional view of one embodiment, respectively.
3 is a sectional view of the magnetic device, FIG. 4 is a characteristic curve diagram of one embodiment, FIGS. 5 and 6 are plan views and sectional views of a conventional example, and FIG. 7 is a characteristic curve diagram of a conventional example. Is. (1) is a dielectric substrate, (2) is a ground conductive layer, (3) is an input side microstrip line, (4) is an output side microstrip line, (5a), (5b); (6a), (6b) )
Is a pair of YIG thin films, (7) is a GGG plate, (8) is a connecting microstrip line, and (9) is a dielectric plate.

Claims (1)

[Claims] 1. A non-magnetic substrate, first and second sets of ferromagnetic thin films formed on both main surfaces of the non-magnetic substrate so as to face each other in parallel, and the first and second sets. Input and output lines formed on the other surface of the dielectric substrate having a ground conductive layer formed on one surface thereof so as to be respectively coupled to the ferromagnetic thin films of the above, and the first and second sets described above. And a magnetic device for applying a magnetic field in a direction perpendicular to each film surface to the ferromagnetic thin films of the first and second sets. Characteristic ferromagnetic thin film filter.